(expand_expr): Update comments and fix formatting.

(expand_expr, case VAR_DECL, STRING_CST, CONSTRUCTOR): If flag_force_addr, put
address in register unless REG.
(expand_expr, case CONSTRUCTOR, CONVERT_EXPR): Make TARGET with TMODE, if
specified.
(expand_expr, case IN_EXPR): Clean up.  Allow INDEX to be an unsigned type.
Always evaluate SET and INDEX in case of side effects.
(expand_expr, case CONVERT_EXPR): Use convert_modes to handle consts.
(expand_expr, case ABS_EXPR): Simplify processing of COMPLEX.
Compare with zero word-by-word if required.
(expand_expr, case ABS_EXPR, MIN_EXPR, COND_EXPR): Don't use TARGET if
not MODE.
(expand_expr, case TRUTH_*_EXPR): Modes of input and output must agree.
(expand_expr, case CONJ_EXPR): Remove redundant def of MODE.

From-SVN: r6794